As is well known in the art, tissue prostheses are often employed to treat or replace damaged or diseased biological tissue. However, despite the growing sophistication of medical technology, the use of prostheses to treat or replace damaged biological tissue remains a frequent and serious problem in health care. The problem is often associated with the materials employed to construct the prostheses.
As is also well known in the art, the optimal prosthesis material should be chemically inert, non-carcinogenic, capable of resisting mechanical stress, capable of being fabricated in the form required, and sterilizable. Further, the material should be resistant to physical modification by tissue fluids, and not excite an inflammatory reaction, induce a state of allergy or hypersensitivity, or, in some cases, promote visceral adhesions. See, e.g., Jenkins, et al., Surgery, vol. 94(2), pp. 392-398 (1983).
Various materials and/or structures have thus been employed to construct prostheses that satisfy the aforementioned optimal characteristics, including tantalum gauze, stainless mesh, Dacron®, Orlon®, Fortisan®, nylon, knitted polypropylene (e.g., Marlex®), microporous expanded-polytetrafluoroethylene (e.g., Gore-Tex®), Dacron reinforced silicone rubber (e.g., Silastic®), polyglactin 910 (e.g., Vicryl®), polyester (e.g., Mersilene®), polyglycolic acid (e.g., Dexon®), processed sheep dermal collagen, crosslinked bovine pericardium (e.g., Peri-Guard®), and preserved human dura (e.g., Lyodura®).
As discussed in detail below, although some of the noted prosthesis materials satisfy some of the aforementioned optimal characteristics, there are several disadvantages and drawbacks associated with the materials.
The major advantages of metallic reinforced prostheses, e.g., stainless steel and Nitinol® meshes, are that they are inert, resistant to infection and can stimulate fibroplasia. Several major disadvantages are fragmentation, which can, and in many instances will, occur after the first year of administration, and the lack of malleability.
Further, many conventional prostheses; particularly, stents are often constructed from various polymeric materials, such as poly(ethylene terephthalate) (PET). Such prostheses often cause irritation and undesirable biologic responses from the surrounding tissues in a vessel.
Although conventional prostheses are designed to be implanted for an extended period of time, it is sometimes necessary to remove the device prematurely, for example, because of poor patency or harsh biological responses. In such instances, the device generally must be removed through a secondary surgical procedure, which can, and in many instances will, result in undesirable pain and discomfort to the patient and possibly additional trauma to the vessel tissue. In addition to the pain and discomfort, the patient must be subjected to an additional time consuming and complicated surgical procedure with the attendant risks of surgery.
More recently, bioabsorbable and/or biodegradable prostheses have been developed in an effort to eliminate the harsh biological responses associated with conventional polymeric and metal vascular prostheses. There are, however, several known disadvantages associated with bioabsorbable and biodegradable prostheses.
One major disadvantage is that the bioabsorbable and biodegradable materials and, hence, prostheses often break down at a faster rate than is desirable for the application. A further disadvantage is that the bioabsorbable and biodegradable materials can, and in many instances will, break down into large, rigid fragments that can cause obstructions in the interior of a vessel.
A further disadvantage associated with conventional prostheses is that existing means for securing the prosthesis into or onto biological tissue within a body vessel have had limited success. Often the securing means comprises engaging the prosthesis to the surrounding tissue by physical or mechanical means, such as disclosed in U.S. Pat. No. 7,918,882. Another securing means comprises modifying the prosthesis surface or material to induce the production of fibrous (scar) tissue to anchor the prosthesis upon implantation within the vessel.
Various polymer based apparatus have also been developed in an attempt to construct reinforced prostheses. Illustrative are the ECM and polymer based apparatus, i.e. grafts and endografts, disclosed in U.S. Pat. Nos. 6,015,432 and 8,142,506.
U.S. Pat. No. 6,015,432 discloses a fiber-reinforced hydrogel prosthesis that is intended to replace cartilaginous materials, wherein the fibers comprise a polymeric material, such as polyurethane fibers.
U.S. Pat. No. 8,142,506 discloses an endovascular tube or bifurcated prosthesis comprising a polymeric material reinforced by a threaded superelastic metal wire, such as a Nitinol®.
A major drawback of the noted polymer based apparatus, as well as most known apparatus, is that the apparatus often comprise or include a permanent structure that remains in the body, i.e. non-biodegradable. As is well known in the art, such structures (or devices) can, and in most instances will, cause irritation and undesirable biologic responses in the surrounding tissue.
Such structures (and devices) are also prone to failure, resulting in severe adverse consequences, e.g., ruptured vessels.
There is thus a need to provide improved prostheses that substantially reduce or eliminate (i) intimal hyperplasia after intervention in a vessel, (ii) the harsh biological responses associated with conventional, and (iii) employ effective vessel securing means.
There is also a need to provide prostheses that can replace or improve biological functions or promote the growth of new tissue in a subject.
There is also a need to provide prostheses that substantially reduce or eliminate the formation of inflammation and infection.
There is also the need to provide prostheses having mechanical compatibility or enhanced mechanical properties. As is well known in the art, a mismatch between the stiffness, hardness, and porosity of a prosthesis in comparison to the surrounding tissue environment can cause irritation and other complications after implantation.
It is therefore an object of the present invention to provide prostheses that substantially reduce or eliminate (i) intimal hyperplasia after intervention in a vessel, (ii) the harsh biological responses associated with conventional polymeric and metal prostheses, (iii) employ effective vessel securing means, and (iv) the formation of biofilm, inflammation and infection.
It is another object of the present invention to provide prostheses that can effectively replace or improve biological functions or promote the growth of new tissue in a subject.
It is another object of the present invention to provide prostheses that include effective reinforcing means for temporarily positioning the prostheses proximate target tissue and retaining strength.
It is another object of the present invention to provide prostheses that can administer one or more pharmacological or therapeutic agents to a subject.